In conventional carburetors, the throttle linkage is not only connected to the throttle valve shaft of the carburetor, but also to an accelerator pump whereby movement of the carburetor linkage to increase the opening of the throttle valve effects operation of the accelerator pump an amount proportional to the increase of throttle plate opening. The accelerator pump is provided in order to insure an adequate supplemental supply of fuel to the induction passages of an associated combustion engine at the time the throttle plate is opened and before an increased flow of air through the carburetor venturi can effect an increase flow of fuel into the carburetor venturi area through the main jet of the carburetor. However, the main jet of the carburetor must, soon after the throttle plate is opened, be capable of delivering sufficient amounts of fuel for proper combustion of the air and fuel mixture during acceleration mode of operation and this is accomplished by an increase of venturi vacuum as a result of an increase in the speed of induction air passing through the carburetor venturi area. On the other hand, after acceleration has been accomplished and continued operation of the engine at speed is carried out at the same throttle opening, the delivery of fuel to the carburetor venturi by the main jet tends to be in excess of that amount which is necessary to support maximum efficiency. Still further, when a carburetor equipped engine is functioning under an engine braking mode, the amount of fuel supplied to the induction passages of the engine through the idle fuel port of the carburetor is totally excessive, inasmuch as no delivery of fuel is needed during an engine braking mode.
Accordingly, a need exists for a carburetor incorporating structure which will be capable of reducing the amount of fuel supplied to the induction passages thereof after cruising speed has been reached and for reducing the amount of fuel supplied to the induction passages of the engine through the idle fuel port of the associated carburetor during engine braking mode operations.
Still further, inasmuch as conventional carburetors utilize an idle fuel delivery system which does not promote atomization of the idle fuel being supplied during idle mode operation, a need exists for a carburetor incorporating structure which will function to more completely atomize or break-up liquid droplets of fuel being supplied to the induction passage through the carburetor idle fuel port.
There have been various forms of fuel economizing jets incorporating air passages formed therethrough whereby the idle fuel supplied to the induction passages of a carbureted engine may be aerated and thus broken up into smaller liquid droplets. One example of this type of jet is disclosed in French Pat. No. 2,307,140 and a second similar type of perforated idle jet screw is disclosed in Venezuelan patent Register No. 29,943. However, these previously known idle fuel controlling jets are effective only during the idle mode of operation of an associated combustion engine and offer no means to reduce main jet fuel discharge during a cruising mode of operation or to reduce the discharge of fuel from an idle fuel port during an engine braking mode of operation.